1. Field of the Invention
The present invention relates in general to a transport system for transporting objects between stations, and relates in particular to improvements in the various active components of a linear motor driven transport system to achieve higher operational performance compared with that of conventional systems.
2. Technical Background
Whenever there is a need to transfer objects such as goods, materials and information in manufacturing lines, transporting of drugs and medical charts in hospitals, various transporting systems have been in use through the years. In these transporting systems, some key components of the system are assembled together to produce a unified transportation system. Some of the components of a conventional transporting system based on a linear motor drive will be explained in some detail in the following under respective headings.
The presentations are divided into eight component groups as follows:
(1) Transport drive, including transport vehicle, carrier and rail track configuration;
(2) Weighing device;
(3) Vehicle stopping device;
(4) Vehicle position detection device;
(5) Primary drive unit structure;
(6) Emergency braking device;
(7) Rail track structure;
(8) Container structure.
Each of the above components will be discussed sequentially in detail with illustrated examples from conventional systems.
(1) Transport Drive
An example of a type of routing in a transport system applicable to the present invention is shown in FIG. 34.
In FIG. 34, a transport vehicle 101 controlled by a command and control device (not shown) runs along an fixed track 102 installed along a transport route. Hereinafter, various components used in the system are referred to as either on the immobile side or on the mobile side. In the following presentation, references are sometimes made to mobile or immobile side of the transport system. This reference is in relation to the two surface of the fixed track, i.e. the mobile side of the fixed track is the side facing the transport vehicle, and similarly the immovable side means the opposite side of the fixed rail.
In some transport systems, a vertical transport route is needed, such as the track 102V shown in FIG. 34, as well as a horizontal track 102H. Such a routing comprises an internally curving track 102C which joins the horizontal track 102H with the vertical track 102V, and an externally curving track 102C' which joins the vertical track 102V with the horizontal track 102H, respectively shown by curved arrows in FIG. 34. Although not shown in this figure, other track configurations, such as inclined tracks and curved tracks which bend within a horizontal plane, can also be provided depending on the need of the transport system.
In FIG. 35, the configurational relationship between the rail track 141 and the transport vehicle 101 driven by such a linear motor driving system is illustrated.
The rail track 141 is provided with a plurality of primary drive units (referred to as LIM1) 142, having components such as the primary winding, disposed at a given spacing along the rail track 141.
The top section of the rail track 141 is formed into a first inclined surface 114U1 and a second inclined surface 141U2 both oriented symmetrically at 45.degree. to the horizontal direction; the bottom section of the rail track 141 is formed into a third inclined surface 141D1 and a fourth inclined surface 141D2 both oriented symmetrically at 45.degree. to the horizontal direction.
A frame member 130 disposed on the container (not shown) of the transport vehicle 101 is driven by a rotation device 131 and is capable of rotating within a given angle.
The secondary conductor member (LIM2) disposed on the linear motor driven system comprises a conductor member 112, for example an aluminum plate, and a magnetic plate 112a fixed on the container of the transport vehicle 101, so as to electrically couple with the primary drive units LIM1. The magnetic plate 112a is for making a magnetic circuit on the LIM2 units, and is made of a magnetic material for example an iron plate having specific capabilities.
There is a top end device 133, disposed on the upper end of the frame member 130, having a first roller 134U1 freely rotatably supported on a first rotation shaft 135U1, and a second roller 134U2 freely rotatably supported on a second rotation shaft 135U2, each being oriented at 45.degree. to the horizontal direction.
The first roller 134U1 rotates on the first inclined surface 141U1 of the rail track 141, and the second roller 134U2 rotates on the second inclined surface 141U2 of the rail track 141.
There is a bottom end device 137 of the frame 131 having a bearing device 139 whose position is adjustable vertically by means of an adjusting screw 138.
The bearing device 139 has a third roller 134D1 freely rotatably supported on a third rotation shaft 135D1 and a fourth roller 134D2 freely rotatably supported on a fourth rotation shaft 135D2, each being oriented at 45.degree. to the horizontal direction.
The third roller 134D1 rotates on the third inclined surface 141D1 of the rail track 141, and the fourth roller 134D2 rotates on the second inclined surface 141D2 of the rail track 141.
In a transport route, such as the route 102H shown in FIG. 34 having an approximately horizontal rail track 141, the weight of the transport vehicle 101 is supported by the first and second rollers 134U1, 134U2, and by operating the adjusting screw 138, it is possible to adjust the dimension of a spacing d1 between the third roller 134D1 and the third inclined surface 114D1, and the dimension of a spacing d2 between the fourth roller 134D2 and the fourth inclined surface 141D2. The dimensions of the spacings d1, d2 may vary depending on the manufacturing tolerances, operating temperature conditions, and the differences in the forming conditions for the straight track and the curved track.
In a vertical transport route, such as the route 102V shown in FIG. 34 having a vertical rail track 141, the spacing between the first roller 134U1 and the first inclined surface 141U1, and the spacing between the second roller 134U2 and the second inclined surface 141U2 of the rail track 141 are adjustable from zero to a maximum value by means of an adjusting screw.
Similarly, in the vertical transport route (102V in FIG. 34), the spacing between the third roller 134D1 and the third inclined surface 141D1, and the spacing between the fourth roller 134D2 and the fourth inclined surface 141D2 of the rail track 141 are also adjustable from zero to a maximum value by means of an adjusting screw 138.
In practice, the spaces d1, d2 are adjusted suitably by adjusting the adjusting screw 138 at the time of setting-up the system for operation, in accordance with the operating requirements so that the transport vehicle 101 can operate stably.
(2) Weighing Device
An example of the transport vehicle 101 suspended from the track 220 is illustrated in FIG. 36.
In this figure, the track 220 is firmly fixed to the frame 222 by the arm 223 through a plurality of rods 221a hanging from the ceiling member 221 of the track 220.
For operating the transport vehicle 101 with the linear motor, an output control device 224 for supplying switched power to the primary winding side of the system is suitably disposed on the frame 222, and on the side facing the transport vehicle 101 of the track 220, primary drive units (not shown) having a sensor are disposed suitably for detecting the arrival and the direction of travel of the primary winding of the linear motor and the transport vehicle.
The transport vehicle 101 shown by the dotted line is supported on each side by four front and the rear rollers 211 straddling the rail track 220.
The secondary conductor member 231 is disposed on the mobile side of the linear motor and is provided with the object sensing capability.
In the transport system having a vertical routing such as the one described above, it becomes difficult to move the transport vehicle upwards when the load on the vehicle becomes too high.
Therefore, there are weighing devices disposed on certain locations of the transport routes for determining the weight of the transport vehicle.
An example of such a weighing device is shown in FIGS. 37 and 38.
FIG. 37 is a cross sectional view of the track 210 where the weighing device is located. The reference numeral 211 refers to each of the four rollers, installed on the vehicle, rotating in contact with the track. The primary windings 218 of the linear motor are suitably disposed along the route 210, including the locations where the weighing device is located, to provide the driving force for the transport vehicle.
That is, the transport vehicle 101 is driven by the power supplied to the primary windings 281 of the linear motor, and moves along the track by being retained by the rollers 211.
Along the target locations on the track 210, the end portion 212a of the first arm 212 is fixed to the track 210 by means of screws 217a. The opposite end portion 212b of the first arm 212 fixed to the track 210 is constructed so as to enable the first arm 213 to slide vertically along a pair of parallel guides 213 shown in FIG. 38.
FIG. 38 shows a plan view of the guides 213 which are fixed to the bracket 214 which is in turn fixed to the immobile side.
Returning again to FIG. 38, a second arm 215 extending downward is joined in parallel to the guide 213 near the opposite end portion 212b of the first arm 212.
In other words, the horizontal thrusting force on the first arm 212, generated by the bending moment from the force of gravity of the track 210, acts on the side surface of the guide 213, but only the vertical component force is transmitted downwards along the guide 213 by the second arm 215.
The lower end portion 215a of the second arm 215 is fastened and joined to the measuring end portion 216a for the weighing sensor, for example a load cell 216, by means of screws 217b.
The fixed end portion 216b of the load cell 216 is fastened and joined to a base 219 formed integrally with the bracket 214 by means of screws 217c, 217d.
The base 219 is fixed to the immobile side (not shown).
The rail track 210 of the above configuration bears the entire weight of the transport vehicle 210 through the rollers 211.
The horizontal thrusting force generated by the bending moment due to the weight of the track 210 including the vehicle weight acts on the side surface of the guide 213, and only the vertical force is transmitted along the guide 213 to the measuring portion 216a of the load cell 216 by the second arm 215 joined to the lower end portion 215a.
Therefore, the lower end portion 215a of the second arm 215 bends the measuring end portion 216a in the turning direction with respect to the fixed portion 216b. A measuring circuit (not shown) transmits an electrical signal which is proportional to the amount of movement of the measuring portion 216a of the load cell 216 corresponding to the load to the control device (not shown) provided on the transport system. The control device (not shown) displays the measured weight according to predetermined conditions, and sounds an alarm when the measured weight exceeds the upper predetermined weight limit.
(3) Transport Vehicle Stopping Device
Next, it is necessary to explain how the system senses and stops the transport vehicle when the vehicle enters a proper position within a target station.
FIG. 39 is a front view of a stopper hook assembly for determining the position of the carrier (relates to a member for attaching the container box) and stopping the transport vehicle in the conventional transport system.
First, the construction of the assembly 301 is explained.
The assembly 301 is fixed to the rail track side of the linear transport system, and comprises: a box-shaped frame 302; a sliding shaft 303 disposed in about the middle of the frame 302; a left and a right slide blocks 304a, 304b mounted on the sliding shaft 303; and coil springs 305 which press the blocks 304a, 304b towards the center of the assembly 301. Spacer blocks 306 are fixed to the frame 302 by means of bolts 307 in the central vertical direction of the assembly 301. The slide blocks 304a, 304b are disposed symmetrically above/below and left/right in the overall view of the assembly, and each is provided with two hook support shafts 308, in the horizontal and perpendicular directions to the axial direction of the sliding shaft 303. Each sliding block 304a, 304b is provided with stopper hooks 309a, 309b, 309c and 309d of an approximately right angle triangle shape disposed freely rotatably around an axial bushing 310. Each of the stopper hooks 309a-309d is attached with a twist spring 311, and the right angle sides of the stopper hooks 309a, 309c slidingly contact the top inside surface 302a of the frame 302 and the side surface 306a of a spacer 306; while those of the stopper hooks 309b, 309d slidingly contact the bottom inside surface 302b of the frame 302 and the side surface 306b of the spacer 306.
The operation of the assembly 301 will be explained next. If a stopper pin 313 fixed in the horizontal direction on the carrier of the linear transport system, is moving from left to right, for example, the inclined surface portion of the stopper hooks 309a, 309b are pressured so that the stopper hook 309a moves counter clockwise in opposition to the force of the twist spring 311, while the stopper hook 309b moves in the clockwise direction in opposition to the twist spring 311. The vertical sides of the stopper hooks 309a, 309b slide against the side surfaces 306a, 306b of the spacer block 306 while the horizontal sides of the stopper hooks 309a, 309b separate from the inside surfaces 302a, 302b, and each of the the arc surfaces 309e slides against the inside surface 302a, 302b of the top and bottom frames, and the slide block 304a moves to the left side along the sliding shaft against the force of the coil spring 305 disposed around the hook support shaft 308. The stopper pin 313 enters the position shown by a double dot line, and stops by hitting the right side stopper hook 309c, 309d. In this case, the rotation of the stopper hook 309c, 309d is blocked by the top and bottom inside surfaces 302a, 302b of the frame, and therefore the slide block 304b moves slightly to the right but is returned to the original position by the force of the coil spring 305.
When the carrier starts moving from the locked position of the stopper pin 313 surrounded by the stopper hooks 309a-309d as shown in FIG. 39, the stopper pin 313 is released from the locked position by the stopper hooks 309a-309d when the overall assembly 301 moves towards the rear of and perpendicular to the plane of the paper. When it is not necessary for the carrier to stop at the position where the assembly 301 is disposed, the assembly 301 is also moved towards the rear of the plane of the paper.
(4) Vehicle Position Detection Device
In a linear motor driven transport system, a carrier rides on the rail track to transport a vehicle from one station to another, and it is necessary that the vehicle be stopped at a precise predetermined position within the station. FIG. 47 shows an example of the conventional device for controlling the carrier position.
In FIG. 47, a carrier 410' is driven by a linear motor having a secondary conductor member 411, and is held on the track and is transported along a ground-based structure 420'.
The carrier 410' is provided with a container 410A, shown by the double dot line, for carrying specified objects, and the container 410A is held on and run on the ground-based structure 420' with a container moving device 410B'. In this figure, illustration of the mechanism for coupling the container 410A with the container moving device 410B' is omitted.
The position of the carrier 410' is determined by a proximity switch 413, provided in a specified location within a station, which reacts to a striker 412. The striker 412 is disposed on the tip end of the first arm 412A provided on the container moving device 410B'.
(5) Primary Drive Unit Structure
FIGS. 40A to 40C show the primary drive units of the linear motor, in which FIG. 40A is a plan view; FIG. 46b is a front view of the unit shown in FIG. 40A; FIG. 40C is a side view of the unit shown in FIG. 40B; and FIG. 41 is a cross sectional side view of the primary drive unit of the conventional linear motor.
As shown in FIGS. 40A to 40C, the primary drive unit is made by punching out rectangular sheet pieces which are laminated into a core 501 of thickness L using a jig; clamping the core 501 with two machine fabricated clamps 502; tightening with bolts 503 and nuts 504; and attaching the assembly to the rail track with bolts of pitch P through the first and second bolt holes on the foot portion 505a, 505b disposed on the extension of the ends of the clamps 502.
(6) Emergency Braking Device
A cross sectional side view of an emergency braking device in the conventional linear motor transport system is shown in FIG. 42, and a partial cross sectional view seen in the direction of the arrow A is shown in FIG. 43.
In the transport system shown in FIGS. 42 and 43, the carrier 602 having a container 601 attached is provided with a carrier frame 604 which has a shape to embrace the rail track 603. The carrier 602 is moved in the horizontal direction (i.e. vertical to the plane of the paper in FIG. 42 by the interaction of the secondary conductor member 605 vertically attached to the carrier frame 604 and the linear motor 606 attached to a vertical plane 603a of the rail track 603. The rail track 603 is supported by the support portion 612 fixed to the fixing member 609. The brake shoe 608 is attached to the tip end of the upper arm 604a of the carrier frame 604 having the stopper pin 607 for determining the carrier position. In addition, a long brake assembly 610 extending in the vertical direction is attached to the fixing member 609 by means of bolts, and a longitudinal air bag 611 (refer to FIG. 43) is thus provided.
If an abnormal situation arises, such as a breakdown in the control system, compressed air is automatically pumped into the air bag 611, and expands the air bag 611, as shown by the double dot line in FIG. 43, and the emergency braking system is designed so that the friction forces between the air bag 611 and the brake shoe 608 stop the carrier 602.
(7) Rail Track Structure
FIGS. 44A to 44C show a first example of the rail track arrangement having the linear motor attached in the conventional linear motor transport system. FIG. 44A is a partial side view; FIG. 44B is a bottom view of the arrangement shown in FIG. 44A; FIG. 44C is a side view of the arrangement shown in FIG. 44B. FIG. 45A to 45C show a second example of the rail track arrangement, including the electrical connections, having the linear motor attached thereto in the conventional linear motor transport system. FIG. 45A is a partial side view; FIG. 45B is a bottom view of the arrangement shown in FIG. 45A; FIG. 45C is a side view of the arrangement shown in FIG. 45B.
In the examples shown above, the components such as the linear motor 702, solid state relay 705, speed sensor 706, terminal stage 703, are attached to both side surfaces of the rail track 701.
It should also be noted that the lead wires 707 provide the electrical connection to other components.
(8) Container Structure
FIG. 46 shows a schematic cross sectional view of the construction of the containers 801-1 and 801-2 in the conventional linear motor transport system. These containers 801-1 and 801-2 are, respectively, provided with a door 802-1 and a door 802-2, only on one side thereof for loading and unloading objects. The container 801-1 moves in the horizontal X-direction on the track 803, and is led into a storage space 805 after passing through a branching point 804 and a straight, short branching track 803a. The container 801-2 moves in the X-direction on the main track 803, and is led into a storage space 805 after passing through a branching points 806, 807 and a looped branching track 803b.
In the storage space 805, there are storage spaces 808, 809 divided by a dividing wall 805a, and the storage spaces 808, 809 are provided with symmetrically disposed left and right stations 810, 811 with respect to the dividing wall 805a at the center. Each of the stations 810, 811 is provided with a center-opening swing door 810a, 811a, and the goods are loaded or unloaded by opening both types of doors, 810a, 811a of the stations on the one hand, and the doors 801-1, 801-2, 802-1 and 802-2 on the containers on the other.
Problems in the Conventional Systems
Problems in the conventional transport systems of the type described above will be discussed separately in the following for each of the components presented above under headings (1) through to (8).
(1) Problems in the Driving Mechanism of the Transport Vehicle
As shown in FIG. 35, the conventional system provided a stable operation of the vehicle, in the vertical and well as in the horizontal directions of the track, by clamping the rail with four rollers which are inclined to fit the edge of the inclined rail. In addition, spaces are provided to accommodate the changes in the dimensions of the rail and other factors of the operation of the tracks.
This type of configuration generated the following problems.
(1-1) When the power is supplied to the primary drive units LIM1, the backing plate (refer to FIG. 35) 112a provided on the secondary conductor member LIM2 is attracted to the LIM1 side, thereby moving the vehicle through a distance equal to the spacing d1 between the track and the rollers. PA0 (1-2) To meet changing conditions of deviations in the spacing (brought about by variations in temperature and assembling precision) between the rail track 141 and each of the rollers, throughout the various sections, such as horizontal, vertical, horizontal curves and vertical curves, it is necessary to finely adjust the spacings d1, d2 by means of the adjusting screw 138. PA0 (1-3) The above situation leads to a time consuming adjustment operation. PA0 (1-4) The spacings d1, d2 change due to the forces of attraction between the LIM1 side and the LIM2 side. PA0 (1-5) The rollers are attached at an angle, which leads to misalignment because of the presence of the spacings d1, d2, thus leading to a problem of snaking of the vehicle. PA0 (1-6) When the dimension of the spacings d1, d2 changes due to snaking, the distance between the LIM1 side and the LIM2 side changes, thus leading to fluctuations in the driving force for the vehicle. PA0 (1-7) The snaking of the vehicle and changes in the spacing d1, d2 lead to vibrations and generation of noises. PA0 (1-8) In the system of the conventional design described above, fine adjustment operations are unavoidable, thus leading to a large number of necessary components and complex structure as shown in FIG. 35 to provide a stable operation of the vehicle. PA0 (1-9) Ultimately, it was difficult to reduce the number of materials needed and the manufacturing costs of the transport system. PA0 (2-1) For the first arm tail end portion 212b to slide smoothly along the guide 213, it is necessary that the two guides 213 be constructed with precision. Therefore, the guide section required not only machining precision of the guide 213 and the first arm leading portion 213a, but also required precision in the assembly. Therefore, both machining and assembly operations became time consuming, and the resulting low productivity prevented lowering in the cost of manufacturing the system. PA0 (2-2) The load measuring sensor (load cell) for the weighing device required precision assembly as explained above, and produced the following problems of assembly. PA0 (5-1) As shown in FIG. 41, spaces G1, G2, G3 are generated between the bolts 503 and the laminated core 501, and between the bolt 503 and the two fabricated clamps 502, and because the spacing are variable, the assembly precision of the two clamps 502 became variable, and the assembly precision of the clamps 502 and the core 501 became variable. PA0 (5-2) Even though it is necessary that the linear motors be installed at the same height, they are not installed at the same height. PA0 (5-3) When the thickness L of the core is altered to meet the thrust requirement of the linear motor, the attachment angle P changes. However, if it is desired to maintain the same attachment angle P, then it is necessary to provide a foot portion of a complex design or to provide unnecessarily large foot portions. PA0 (6-1) It is necessary to provide a vertical brake assembly having air bags separately from the rail track. PA0 (6-2) The position of attaching the air bag must be adjusted on site. PA0 (6-3) The weight of the vehicle moving on the rail is increased because the brake shoe is attached thereto. PA0 (7-1) Because various devices are attached to both surfaces of the rail track, start-up adjustments become time consuming. PA0 (7-2) Because various devices are attached to both surfaces of the rail track, there is an increase in the number of interconnect of the lead wires, and leads to an increase in the fabrication and assembly steps. PA0 (7-3) Because both surfaces of the rail track are provided with precision devices, it is necessary to pay special attention to handling of the components for the rail tracks for shipping.
For this reason, in the curved sections of the track, for example, there is a danger that the surfaces on the LIM1 side and on the LIM2 may come into contact with each other. If the distance of the spacing d1 is made larger to avoid the contact of the surfaces, the system then became vulnerable to unstable motion, such as snaking, and depending on the operating condition, the forward thrust force is degraded.
Specifically, if the spacings d1, d2 are to be adjusted to a target distance of 0.15 mm, the finished dimension of d1, d2 ranges between 0.1 to 0.2 mm. However, it is a difficult task to make an on-site adjustment to a heavy and complex structure in an ill-equipped environment, and depending on the conditions of the track, it may be necessary to make several adjustments before the system can operate smoothly.
(2) Problems in the Weighing Device
There are following problems in the conventional weighing devices.
(a) The measuring end of the load cell and the second arm are connected with screws, and attention is required so as not to pre-load the load cell.
(b) The measuring end of the load cell and the second arm are connected with screws, and there is a danger of breakage due to excess force being applied to the load cell during transport of goods.
(c) The load cell is installed with the load cell in a horizontal position, and such an arrangement wasted critical spaces and results in a large weighing device.
(3) Problems in the Vehicle Stopping Device
The conventional design of the vehicle stopping device including the stopper hook assembly presented the following problems.
The arc shaped section of the hook portion of the assembly is relatively difficult to fabricate; because
it is necessary to attach four twist springs to each of the four stopper hooks; and PA1 machining precision of the inside surface of the top and bottom surfaces of the frame member must be high because the rotation of the stopper hooks brings them into direct contact with these surfaces. PA1 (a) a rail track erected along a transporting route having branching routes; PA1 (b) a plurality Of linear motor driven transport vehicles moving along the rail track; PA1 (c) a plurality of stations disposed at suitable locations along the route; PA1 (d) at least one weighing device disposed on the plurality of stations; PA1 (e) a vehicle stopping device including a stopper hook assembly disposed on each of the plurality of stations; PA1 (f) a vehicle position detection device, disposed in the vicinity of the plurality of stations, comprising the stopper hook assembly cooperating with the vehicle stopping device; PA1 (g) an emergency braking device disposed on non-horizontal rail tracks; PA1 (h) a container associated with the transport vehicle for loading and unloading the goods; PA1 (i) a scheduling controller for controlling the movement of the plurality of transport vehicles between the plurality of stations, wherein at least the components (e), (f), (g) and the primary drive unit are wholly or partially disposed on one side of the fixed rail track of the transport system so as to enable efficient servicing of components and offer reliable control of the vehicle in the transport system.
(4) Problems in the Vehicle Position Detection Device
In the conventional design of the vehicle position detection device, it is necessary to provide a first arm 412A for attaching the striker 412 for operating the proximity switch 413.
It is extremely difficult to provide spaces for providing striker and stopper hole within a limited available size and spaces of the peripheries of the carrier structure, and it makes the ground based structure 420' complex, and prevented lowering of the cost of producing the system.
(5) Problems in the Primary Drive Unit
The conventional design of the primary drive unit shown in FIG. 40A presented the following problems.
(6) Problems in the Emergency Brake
The conventional design of the emergency braking device shown in FIG. 42 presented the following problems.
(7) Problems in the Rail Structure
In the conventional design of the rail structure, the following problems are presented.
(8) Problems in the Container Structure
The conventional containers are provided with doors 802-1, 802-2 only on one side. For this type of door configuration, a short straight branching route 803a is acceptable when the container 810-1 is to be led into station 810. However, when the container 801-2 is to be led into station 811, it is necessary either to set up a looped branching route 803b as shown in FIG. 46 or to provide a short straight route (similar to route 803a), and the container must be passed through the branching point 806 once, and then the container must be reversed from the branching point 806 to enter the straight route. Therefore, when looped routes are necessary, not only the overall cost of installing the linear motor transport system increases, but there is also a necessity to secure sufficient area for installing looped branching routes. Further, complex control operations are necessary for reversing the container from a branching point to let the container enter a straight route.